1. Field of the Invention
The present invention relates to a method of manufacturing a door for a vehicle and a door manufactured by the same, and more particularly, to a method of manufacturing a door with reduced weight, and thus a reduced manufacturing cost.
2. Description of the Related Art
Generally, a vehicle frame door constitutes the frame structure of a door. As illustrated in FIG. 1 (RELATED ART), the vehicle frame door includes a door frame assembly 1, which defines a space to be opened or closed by a door glass, and a door outer panel 2 and a door inner panel 3, which respectively form the outer contour and the inner contour of the door.
The door frame assembly 1 serves as a window frame in which the door glass is installed, and includes a frame portion and a rail portion. Here, the rail portion is a portion into which the edge of the door glass is inserted so that the door glass, which is movable upward or downward to open or close a window, is guided along the rail portion.
The door outer panel 2 and the door inner panel 3 are spaced apart from each other by a predetermined distance in the width direction of a vehicle, and at least portions of the peripheries of the door outer panel 2 and the door inner panel 3 are coupled to each other via bonding such as, for example, hemming or welding, thereby forming a closed cross section having a section coefficient that satisfies the required rigidity of the door.
Conventionally, the outer panel 2 and the inner panel 3 of the door are manufactured by, for example, a pressing process using steel (i.e. a steel sheet), and are then assembled with each other.
In addition, an impact beam 4 is installed between the door outer panel 2 and the door inner panel 3 so as to increase the rigidity of the side surface of the door in order to improve the collision performance of the side surface.
The impact beam 4 is a reinforcement beam that is installed to increase the strength of the door against side surface collisions. The impact beam 4 may be installed on the door inner panel 3 as both ends of the impact beam 4 are secured to the door inner panel 3 by means of beam brackets 5.
In addition, a door member 6 may be mounted to the door inner panel 3, separately from the impact beam 4. The door member 6 mounted to the door inner panel 3 and the door outer panel 2 located at the outer side of the door member 6 are in contact with each other, or are bonded to each other using, for example, a sealant or an adhesive.
As such, the door member 6 serves to prevent vibrations or shaking of the door outer panel 2 that may occur during driving, and also serves to prevent bending of the door outer panel 2 due to, for example, slight shocks.
In addition, for example, a belt outer panel 7 for increasing the strength of a door belt line, or a door hinge (not illustrated) may be installed.
In the related art, the respective elements constituting the frame door have been manufactured using steel. For example, as illustrated in FIG. 2 (RELATED ART), the door inner panel 3 may be manufactured by molding a steel sheet, such as a tailor welded blank (TWB), in a mold (e.g. a single mold).
Here, a TWB is manufactured by cutting sheets, which have, for example, different thicknesses and strengths and are formed of different materials, into an appropriate size and shape, and then, bonding the sheets to each other by, for example, mesh seam welding, plasma arc welding, or laser welding. The inner panel 3 may be completed by molding one piece of TWB.
Meanwhile, in order to reduce the weight of the vehicle, the elements constituting the door need to be manufactured using lightweight materials.
When moving elements of the vehicle, such as the door, are reduced in weight, in addition to reducing the weight of the vehicle, the center of gravity of the vehicle may be lowered and the moment of rotational inertia may be reduced, which may increase the stability of driving and the merchantability of the vehicle.
There is known technology for manufacturing the respective elements of the door using aluminum materials. The weight of the door may be reduced when the respective elements of the door are formed of aluminum materials and, for example, a pressing, roll-forming, extrusion or bending process is optimal.
For example, in the case of the door inner panel, as illustrated in FIG. 2, respective parts of the door inner panel are molded separately in respective molds (e.g. two molds) using two aluminum alloy sheets, and thereafter the molded parts are bonded to each other via, for example, riveting, adhesive attachment, or welding so as to complete the integrated door inner panel 3.
Alternatively, the door inner panel may be molded in a single mold using a TWB formed of aluminum materials.
However, when the door inner panel is manufactured using aluminum materials, there are several problems such as, for example, limitations on the molding ability, welding ability, and bonding strength, increases in the level of difficulty and the level of complexity in the process of molding the respective elements, and increases in the number of molds used and mold costs and, consequently, the overall costs of the respective elements.